Downhole actuation system

ABSTRACT

A downhole actuation system wherein a counting sleeve comprises at least one radial opening in which at least one seat element is arranged, the at least one seat element being capable of taking up a first, active position in which the at least one seat element projects into a longitudinal through-channel of the counting sleeve and a second, passive position in which the at least one seat element is retracted from the through-channel, the at least one seat element in its first position forming an annular seat configured to engage the actuating body.

The present invention relates to a downhole actuation system for use with a well, for example a petroleum well.

BACKGROUND

An oil well normally consists of one or more pipes within one another that are run down a borehole, the outer layer or layers known as a “casing”, an inner production tubing extending virtually the length of the borehole, and control lines. The casing protects the inner production tubing and holds the formations surrounding the well in place so that they do not collapse into the well. They also protect against unwanted inflow of fluids from the surrounding formations.

During the completion and start-up of gas and oil wells it is in some cases necessary to carry out a fracturing job or other operations. When a fracturing job has to be done, it will typically be required to pump a fluid into the reservoir under high pressure so as to cause the shale or formation to fracture. This is done to obtain a large surface down in the formation through the fractures so as to allow the gas or oil to flow more easily in towards the production tubing.

When this type of job is to be done, it is important to maintain good control of the pressure of the different zones in the well, and it can also be difficult to pump sufficiently large volumes of fluid into the well in order to obtain the required pressure, simply because the well constitutes a large volume.

It is therefore common to divide to the well into zones. Today, this is normally done by using rubber elements that swell up in contact with hydrocarbons or water. These rubber elements are usually mounted on the exterior of the production tubing that is run into the well in the reservoir. The rubber elements thus swell up against the formation (the well wall) and form a seal between the formation and the tubing. If several such seals are put in place, the well will be divided into a plurality of closed-off zones between them.

To be able to produce the well, it is in addition usual to install one or more valves capable of being opened and closed between two such rubber elements that will form a zone, the purpose of this being to give the oil/gas an opening in the tubing through which to flow, and to make an opening through which the fracturing fluid can flow out during the fracturing job. The division into zones means that it is only necessary to pump a small amount of fluid into the well. The use of such rubber packers and valves simplifies the fracturing jobs, and there is no need to increase pressure in the whole well, but only in the area between two packers that constitutes a zone. This is done in that the valve or valves in the production tubing are opened in a zone between two packers, whilst the rest are kept closed. In this way, the well can be fractured or produced selectively, with the option of closing off ingress of water that occurs in another zone by closing the valves.

Another method is to form zones by pumping cement down through the production tubing and up through the space on its outside such that the tubing is cemented firmly to the formation. This cement is pumped down the production tubing from the surface and all cement is forced out of the tubing and up through the space on its outside in that a cement dart is pumped down after the last cement and forces all the cement down ahead of it when it is pushed down in the tubing by fluid pressure applied from above. The tubing is open at the end and the cement will now flow out from this opening and up through the space between the formation and the tubing. This will empty the inside of the tubing of cement and at the same time cement it firmly to the formation on the outside.

The production tubing can also now comprise a plurality of valves along the tubing that can be opened. The division into zones will be accomplished by using cement that seals the space between the tubing and the formation, after which one or more valves are opened such that a pressure is applied from the surface which is sufficiently high to fracture the cement in the immediate vicinity of the valve that is open, but not sufficiently high to fracture the cement of the nearest adjacent valve. In this way, the well is also divided into zones.

The number of such zones and the number of valves in each zone varies according to the well conditions, but it is common to have 5 to 30, with each zone, for example, comprising up to 10 valves.

These valves can normally be opened/closed using a wireline intervention tool, or they can be opened by dropping a ball or another body into the production tubing in the well, which then comes to a stop in a valve seat. The pressure is then increased above the ball and a slide or sleeve is pushed down to open the valve. Normally this is achieved in that the valves arranged uppermost in the tubing have a seat of large diameter, the seat diameter being reduced successively downwards in the well.

By first dropping a small ball into the production tubing, the ball will pass through the ball seats of the upper valves (which have a large diameter) and then land on a valve seat in the lower part of the well that is adapted to the diameter of the ball.

The right valve can thus be selected based on the diameter of the ball. However, such a system creates restrictions and a successive narrowing downwards in the well. This will also be the case if forms of actuating bodies other than balls are used.

The conventional methods and systems comprising different seat diameter, restrictions and narrowing, are disadvantageous in view of the operations that are to be carried out later in the well. These operations can, for example, include well logging, placement of plugs to close off a section permanently etc., or simply that the restrictions in the tubing constitute production choking. These drawbacks often result in the ball seats having to be drilled out, which involves costly operations with the aid of coiled tubing after the fracturing job has been done, to ensure that the production tubing in the well has a uniform inner diameter without restrictions and constrictions.

Patent application EP 2 360 347 A2 relates to a system where different ball sizes have to be used for each zone. It is based on two sleeves for actuation, an inner sleeve containing a loose ball seat that is fastened inside an outer sleeve by some shear pins. When the ball lands on the seat, both sleeves will move down until a shear pin is broken and the ball is released and moves down to the next valve where the operation is repeated, and then continues downwards such that all the zones open.

Today, there are two solutions where balls of the same diameter can be used in all the zones. One of these solutions has an external indexing system that causes the sleeve to rotate, also known as a “jay slot system”, as described in US 2013/0248201. This allows the balls to fall until the desired number of rotations/indexations of the sleeve has been obtained. Typical for such systems is that the largest number of rotation points is on the upper sleeves and the smallest number on the lower ones. These systems are expensive and complicated to produce and set up (install), and it is particularly costly to mill the external groove in the sleeve that is to cause rotation.

The system is also very sensitive to contaminants and impurities in the well fluid that will enter the grooves and the spring pocket, resulting in the system locking completely. It is also difficult to reset the system if it is desired to carry out a new fracturing or acid stimulation job, or close the zone.

Another known system is taught in GB 2506265. This system has similar drawbacks as the solution mentioned above.

It is an object of the present invention to provide a downhole actuation system which provides advantages over known solutions and techniques in the above-mentioned or other areas.

SUMMARY

In an embodiment, there is provided a downhole actuation system, designed to be actuated by means of an axial movement of a counting sleeve, where the counting sleeve is arranged in a pipe section in a well, the pipe section forming a housing for the counting sleeve, where the axial movement of the counting sleeve is designed to be initiated by an actuating body in the pipe section, wherein the counting sleeve comprises at least one radial opening in which at least one seat element is arranged, the at least one seat element being capable of taking up a first, active position in which the at least one seat element projects into a longitudinal through-channel of the counting sleeve and a second, passive position in which the at least one seat element is retracted from the through-channel, the at least one seat element in its first position forming an annular seat configured to form a seat for the actuating body.

The appended claims outline further embodiments.

BRIEF DESCRIPTION OF THE DRAWINGS

An illustrative, non-limiting description of embodiments will now be presented with reference to the appended figures, wherein:

FIG. 1a shows a side view of a subterranean borehole provided with a number of valve units according to an embodiment of the present invention,

FIG. 1b shows a side view of a subterranean borehole provided with a number of valve units according to another embodiment of the present invention,

FIG. 1c shows a side view of a valve unit according to an embodiment of the present invention,

FIG. 2 shows the valve unit illustrated in FIG. 1c with an actuating body landed on a ball seat,

FIG. 3 shows an embodiment of a counting sleeve which may be used in a valve unit,

FIG. 4 shows a close up detail of an actuating body that has landed on an embodiment of a ball seat according to the present invention,

FIG. 5 shows another close up detail of an actuating body that has landed on an embodiment of a ball seat according to the present invention,

FIG. 6 shows a close up detail of a valve unit according to an embodiment of the present invention,

FIG. 7 shows a side view of a valve unit with an actuating body landed on a ball seat according to an embodiment of the present invention,

FIG. 8 shows the valve unit illustrated in FIG. 7 with an actuating body landed on a ball seat,

FIG. 9 shows a side view of a valve unit with an actuating body on its way to a ball seat according to an embodiment of the present invention,

FIG. 10 shows a side view of an embodiment of a valve unit according to the invention in an open position,

FIG. 11 shows various views of an embodiment of a valve unit in an open position according to the invention,

FIG. 12 shows a close up detail in side view of a valve unit in an open position of an embodiment according to the invention,

FIG. 13 shows a side view of a valve unit with an actuating body landed on a ball seat according to an embodiment of the present invention,

FIG. 14 shows a close up detail in side view of an embodiment according to the invention,

FIG. 15 shows a close up detail in side view of an embodiment according to the invention,

FIG. 16 shows a side view of a valve unit with an actuating body landed on a ball seat according to another embodiment of the present invention,

FIG. 17 shows a side view of a valve unit with an actuating body in various positions according to another embodiment of the present invention,

FIG. 18 shows a side view of a valve unit with an actuating body in various positions similar to FIG. 17,

FIG. 19 shows a detailed side view of an alternative ball seat solution according to an embodiment of the present invention,

FIG. 20 shows a detailed side view of an alternative ball seat configuration according to an embodiment of the present invention,

FIG. 21 shows a further side view of the alternative ball seat configuration shown in FIG. 20,

FIG. 22 shows a side view of a valve unit with a further alternative ball seat configuration according to an embodiment of the present invention, and

FIG. 23 shows a perspective view of the embodiment shown in FIG. 22.

DETAILED DESCRIPTION

Illustrative embodiments related to actuation of different types of valves will now be described. It should, however, be understood that the downhole actuation system may be employed for actuation of various other functions and operations in different types of tools or equipment.

FIGS. 1a-c show a borehole 100 for a well 101 that extends down through an oil/gas-bearing formation 102, and where a production string 104 extends down in the well. It can be seen that the well 101 first extends vertically and then bends into a horizontal direction.

FIG. 1a shows an example where nine valve units or pipe sections 1 are installed in the well in order, section by section, to be able to pump fluid into the formation 102 to make it ready for the production of oil/gas.

An actuating body/ball 3 of a single size is dropped or pumped into the well and will land on a ball seat 4 in a valve unit. This is, inter alia, shown in FIG. 4. A constriction or cam 30 presses a plurality of ball seat elements 5 in the annular ball seat 4 inwards and creates a seat that prevents the ball 3 from continuing downward in the well. When the first ball 3 is dropped into the well 101, it will land on an actuated annular ball seat 4, which annular ball seat 4 is located in a counting sleeve 2.

This can be achieved in that the system consists of an actuation system that preferably only has one internal, axially movable counting sleeve 2. The internal, axially movable counting sleeve 2 has one or more actuatable annular ball seats 4 comprising ball seat elements 5 capable of moving into and out of a wellbore. How this takes place is explained in more detail below.

There may be some leakage past the ball 3, the annular ball seat 4 and the counting sleeve 2 wall, but this is marginal compared with if the ball 3 had not been present on the annular ball seat, and has in practice been found to be of little significance. In most cases, it is not necessary to form an entirely sealed connection between the ball 3, the annular ball seat 4 and the counting sleeve 2 wall, but rather establish a flow restriction that allows build-up of fluid pressure above the ball 3.

According to this embodiment, an axial displacement of a counting sleeve 2 will be effected when larger pressure is formed above the actuating balls 3 that have come to rest on an annular ball seat in a valve. When the counting sleeve is axially displaced, the ball seat elements 5 in an annular ball seat 4 will retract and the ball 3 will be capable of being pumped further down to the next annular ball seat 4 in the valve below, where the same procedure takes place (i.e., an axial displacement of the valve's counting sleeve), until the number of predetermined clicks in a valve has been reached and the valve(s) opens/open. When a ball 3 is retained by an annular ball seat 4 in a counting sleeve 2, this pressure will, as mentioned, displace the counting sleeve 2 axially and thus displace the counting sleeve by one click.

According to one embodiment, the counting sleeve 2 is designed to regulate flow out and in through the valve openings. One such use may be to seal against flow through the openings of a pipe section until the counting sleeve 2 has counted the correct number of actuating balls (number of “clicks”), in other cases, the purpose may be to shut off flow through the openings of the pipe section after the correct number of actuating balls has been counted. It should again be understood that the counting sleeve could also be used to actuate other operations or functions, or actuate a sequence of operations or functions.

In an exemplary embodiment of a well comprising a plurality of valves that is divided into five zones, the uppermost valves seen from above looking down into the well will typically have respectively: five ball seat element rings with an actuatable annular ball seat 4, then four, three, two and lastly the lowermost set which will typically have one annular ball seat 4. Such a configuration will provide a system where the bottom valve (set) is actuated first, then the next and the next etc. As mentioned, the sequence may be different if desired.

According to an embodiment, the system can be so designed that all valves 1 that are run into the well as a part of the production tubing are in an actuated position. In that case, that means that at least one annular ball seat 4 is actuated in each valve's counting sleeve 2. In this way, all the counting sleeves in the successive valves will immediately be displaced axially in one step when the first ball passes through the valves.

In the aforementioned exemplary embodiment, when a ball 3 passes through the uppermost valve, it will typically displace the inner counting sleeve 2 one step or click, in order then to allow the ball 3 to fall freely downwards in the well. When the ball 3 has displaced the counting sleeve 2 in the upper valve by one click axially and released the ball, the next subsequent annular ball seat 4 in the counting sleeve 2 in this valve will be actuated.

In the aforementioned exemplary embodiment, the valve or valves arranged lowermost in the well will typically be designed to open out towards the formation when the first ball 3 passes through the row of counting sleeves 2 that are located above the lowermost valve or pipe section 1.

Actuation and de-actuation of each annular ball seat 4 takes place in that the counting sleeve 2 has at least one group, row or ring of radial and circumferential throughbores or holes 6. In each of these there is typically installed ball seat elements 5 from the exterior of the sleeve 2. The ball seat elements 5 installed in this group of bores or holes 6 will not be able to fall out through the holes 6 and into the tubing as the holes will have a smaller diameter than the ball seat elements 5. This means to say that each hole 6 has a diameter that can be essentially constant through the bore, apart from the end of the bore that opens in towards the wellbore, this end being provided with a constriction which ensures that a ball seat element 5 cannot fall out of the bore and into the wellbore. According to an embodiment, the ball seat elements 5 have a larger diameter than the radial thickness of the counting sleeve 2, i.e., a larger diameter than the body of the counting sleeve. This ensures that the ball seat elements 5 either project slightly into the wellbore (and thus can form an annular ring seat 4), or slightly out on the exterior of the counting sleeve (such that it can be held in a groove, pushed out of the wellbore, pushed into the wellbore with the aid of a constriction or cam 30 etc.).

When the annular ball seat 4 formed by the groups of radial and circumferential bores 6 and ball seat elements 5 is not in the active position, the ball seat elements can be able to travel freely in the bores in the counting sleeve 2 out towards the inner wall of the pipe section. This is because the pipe section 1, in the area around the non-active annular ball seats, has an internal diameter greater than the external diameter of the counting sleeve 2, such that a space is formed between the pipe section and the counting sleeve 2. The ball seat elements 5 will not be able to fall out, but will be able to travel a limited distance outwards such that they do not constitute a restriction inside the counting sleeve 2. This travel will typically be limited to, for example, slightly less than half the ball seat element's diameter. By limiting the travel to less than the ball seat element's half diameter, the ball seat elements are prevented from falling out of their respective holes 6 in the counting sleeve and into the space between the counting sleeve and the pipe section.

The annular ball seat 4 is actuated by the counting sleeve 2 either being displaced axially relative to the pipe section 1 that houses the actuation mechanism. Actuation takes place in that the pipe section 1 has an internal cam or constriction 30 that causes the ball seat elements 5 to be pushed partly out into the wellbore. These ball seat elements 5 are typically arranged in a ring, i.e., form a ball seat that comprises a ring of ball seat elements 5.

When a counting sleeve 2 is displaced axially by a ball 3 lying on an active annular ball seat 4, the groups of ball seat elements 5 in the annular ball seat 4 in the relevant counting sleeve 2 will also be displaced axially, the group of ball seat elements 5 located in the space between the pipe section and the counting sleeve just above the internal constriction or cam of the pipe section being pressed partly out when the group or row of radial, circumferential bores and ball seat elements pass the constriction or cam. The ball seat elements, which now are pressed partly out into the wellbore, will create a restriction constituting an annular ball seat that the ball is unable to pass.

At the same time as this new annular ball seat is now formed by the ball seat elements in that they are pressed partly inwards (into the wellbore) by the pipe section constriction or cam, the ball seat elements in the annular ball seat previously actuated, i.e., the previous annular ball seat located on the pipe section's internal constriction or cam when the previous actuating ball (previous click) reached the actuation mechanism, will be free to be pushed partly out into the space around the counting sleeve below the constriction or cam, the actuating ball that rested on the previous annular ball seat being allowed to proceed further down in the well. The actuation mechanism will now have undergone one displacement or a click and be ready to receive and stop the next actuating ball, after which the same can happen again or the final actuation.

In the new space below the constriction or cam 30 between the counting sleeve 2 and the valve or pipe section 1, the ball seat elements 5 will have the possibility of collapsing or retracting such that the internal restriction in the counting sleeve which constituted the annular ball seat 4 is removed and allows the actuating ball 3 to fall further down in the well. The actuation mechanism has now counted a passing actuating ball whilst the counting sleeve is displaced axially to the next position, wherein a new annular ball seat is formed.

In some cases, it is conceivable that the actuating balls 3 will be pumped so quickly and forcefully down the well (high pressure) that the ball seat elements lying in the annular ball seat 4 do not manage to collapse fast enough into the space between the counting sleeve 2 and the valve or pipe section 1 below the constriction or cam 30, such that the counting sleeve is displaced too far down and, for example, two displacements/clicks, one and a half or finds another unfavourable intermediate position. This is not desirable because count can be lost or the counting sleeve/ball may get stuck. The ball per se will decompose, but then it will not have passed through the valves below, such that the row of valves is out of synchronisation. A similar situation may arise if impurities get into the space between valve and counting sleeve such that there is no room for the ball seat elements to collapse into, with the same result that the valves are left in a non-controllable position.

According to one embodiment of the invention, this can be avoided in that above (or another suitable point on the counting sleeve) the bores and the ball seat elements that constitute the annular ball seat in the counting sleeve, there is bored one or more new holes 13 for one or more elements 14 (FIGS. 3 and 4), which per se may resemble or correspond to the different types of ball seat elements 5 mentioned in this document. These holes 13 and the elements 14 will be able to have the same or partly similar properties as the ball seat elements 5 and the holes 6 that constitute the annular ball seat 4. The position of these additional bores or holes will advantageously be at the point that forms the largest diameter D of the actuating balls 3, i.e., that the actuating ball will block the bores or holes at its largest diameter D and thus press the ball seat elements out into a space between pipe section and counting sleeve, e.g., in the form of groove 15 or the like.

This at least one element 14, which now is pressed out (in the groove 15 or the like), will not be able to pass the internal constriction or cam 30 in the valve or the pipe section 1 which typically runs 360 degrees around in the pipe section 1 (FIG. 5). Optionally, the groove 15 may have a determined length, where the lower end of the groove forms a seat or a stop. Such a design will result in the counting sleeve then being wholly or partly locked against further axial movement, as the actuating ball rests against an actuated annular ball seat 4 which is on the pipe section 1 constriction or cam 30 whilst the actuating ball 3 presses the ball seat element or elements 5 out above the pipe section constriction or cam 30, optionally the lower end of the groove which forms a seat or a stop. Axial movement will then not be possible.

In this position the elements 14, which are pressed out (in the groove 15 or the like), will prevent the counting sleeve from being carried along to an uncontrollable or unfavourable intermediate position, and that they are released as soon as the underlying ball seat elements in the annular ball seat collapse into the space between the valve housing and the counting sleeve. Above such travel stop elements, a new annular ball seat will have reached active position as a new ring of ball seat elements has come onto the pipe section cam.

According to one embodiment of the invention, the counting sleeve can also be locked against unwanted rotation in that one or more grooves 15 are cut out in the pipe section constriction or cam 30, which are through-going and which correspond with a steering mechanism in the counting sleeve that follows this cut-out or groove. This rotation-preventing groove 15 may be the groove mentioned above or comprise separate, dedicated grooves and one or more elements 14.

In FIGS. 1-19 the ball seat elements 5 are shown as spherical balls. It should be understood that these spheres are only used as examples to illustrate the invention. Elongate dogs, split sleeves, ellipsoid elements, square elements, semi-spherical elements, oval elements, cylindrical, conical etc., rods or other suitable geometries that have the property that they can slide in and out of holes in the counting sleeve holes, are all possible alternatives to spheres. FIG. 19 shows one such alternative embodiment form comprising dogs.

In FIGS. 1-19 the bores or holes 6 are shown as radially extending bores or holes, i.e., perpendicular to the axial direction of the wellbore. It should be understood that this is only a possible embodiment used as an example to illustrate the invention. FIGS. 20 and 21 show alternative configurations of the bores or holes 6, the bores or holes 6 being angled (i.e., an angle less than 90 degrees relative to the axial direction of the wellbore). Other angles and directions are possible. Considerations that may form the basis for different configurations of angles and directions may include force distribution factors, deformation as a result of the application of large forces, impacts etc. If the ball falls into the annular ball seat with sufficiently large force, the geometry of the ball seat elements 5 and the holes 6 will be of major importance in relation to how and where forces are transferred. In embodiments corresponding to those shown in FIGS. 1-18, a large portion of the forces that strike the annular ball seat when the ball lands, is transferred to the housing or the pipe section around the counting sleeve, which may result in damage/deformation. By selecting alternative geometries, e.g., other types of ball seat elements and/or angled holes, forces can be distributed such that, for example, the counting sleeve absorbs a larger portion of the forces. If the counting sleeve takes up a larger portion of the forces, it will in turn be able to distribute forces to the grooves 15, the cam 30, or other stop elements. Such a design can also be advantageous if it is found that the counting sleeve or other elements have a tendency to become stuck (deposits, corrosion etc.), because the counting sleeve may have applied thereto a larger force that jerks it free or overcomes unexpected frictional forces.

It should be understood that “pipe section 1” and/or “housing” in this connection comprises the pipe or the material around the counting sleeve 2, in relation to which this sleeve is displaced. This pipe or material is primarily motionless. According to an advantageous embodiment, the only next moving parts in the system are the counting sleeve and the ball seat elements that are used to form the annular ball seat 4. The valve per se may comprise other moving parts, depending on what function or functions it is to have or operations it is to perform.

In this document, the actuating body is referred to as a ball 5, but it should be understood that other actuating bodies that can be dropped, pumped or run down the wellbore are also included, e.g., a dart. Reference is also made to actuation system and actuation mechanism. These terms are used somewhat interchangeably.

As mentioned, it is conceivable that the ball seat elements that are pressed out are not sufficient to prevent double counts, as the ball seat elements in the rings that are above and below the active annular ball seat 4 may project out slightly and cause restrictions that can result in friction between passing actuating balls and the counting sleeve, which may lead to an unintentionally long axial movement of the counting sleeve. According to an embodiment of the invention, this can be avoided in that, for example, friction-creating elements 16; 17; 18 are installed in the form of e.g., a split ring between the counting sleeve and the pipe section, which creates friction between the counting sleeve and the pipe section that is so large that only a ball lying on one active annular ball seat on the pipe section constriction or cam will be capable of moving the valve's counting sleeve (FIG. 14). This can be controlled in that during pumping of the actuating balls pressure build-ups can be monitored and a check can be made of correct pressure build-up above the balls down through all the valves. By correct pressure build-up is meant the pressure required above the ball to overcome the retaining power of this split ring. If such pressure build-ups are registered as correct for all the valves throughout the well, it will be possible to establish with reasonable certainty that all the counting sleeves have correctly counted the number of balls and thus carried out the correct number of displacements/clicks. Other friction-creating elements are also conceivable, e.g., a rough surface, a coating, ridges, c-clip rings, shear rings, shear pins.

According to an embodiment, this can be achieved by equipping the last valve in each zone with a travel stop such that the counting sleeve is not allowed to travel so far in the pipe section that an actuating ball is dropped from the annular ball seat on the constriction or cam in the pipe section. This travel stop can in its simplest embodiment comprise an edge or shoulder 50, such that the lower end of the counting sleeve stops physically against this in the pipe section before the annular ball seat 4 reaches the end of the constriction or cam 30 in the pipe section (FIG. 18). In this way, the annular ball seat in this valve will retain the actuating ball and block against flow down past the actuating ball. This last valve or pipe section 1 in a zone must also be adjusted with regard to positioning of openings in valve housing and counting sleeve such that these coincide and are open in such an end position.

A potential use of the invention is the possibility of forming or shutting off communication between the wellbore and the environment around the well, i.e., a valve. It should be understood that the use of the actuation system according to the invention in connection with a valve is only one example, as many of the functions and considerations can be used or be relevant for other applications.

A plurality of valves comprising an actuation system will be capable of being arranged at regular or irregular intervals downwards in the well, the number of displacements or clicks for which the actuation mechanism is designed will determine how many balls must be dropped to actuate the valve. The different valves that are arranged downwards in the well can be actuated after a desired number of passing balls. When the lower valves in a well have been opened, fluid will typically be pumped out through the opening in the pipe section and into the reservoir. When this operation is complete, the next ball is dropped into the well and this will then typically open the valve or valves in the overlying zone in the well. It is then desirable to pump fluid out through openings in the valve houses in this new zone and not in the zone that has already been treated or above the zone or zones above the new active zone. However, the sequence may be varied, e.g., in that some valves are opened whilst others are closed. The valves can also be opened and/or closed in graduated steps, e.g., in that each ball and each click gives a larger or smaller valve opening.

The valve openings can comprise radial holes in the counting sleeve that overlap corresponding radial holes in the surrounding pipe section when the actuation mechanism has performed the number of desired displacements or clicks. Other embodiments or positions of valve openings are also conceivable.

Other uses of the invention may comprise actuating different tools, functions or operations downhole in the well.

Further, it may be an advantage if the valve's inner counting sleeve is equipped with at least one industry-standardised profile for connection of a well tool. By a profile is meant typically an internal cut-out. One such profile will preferably be arranged at each end of the counting sleeve, one at the bottom for opening by means of well tools and one at the top for closing.

When all the valves in all the groups have been opened and, for example, a fracturing job has been carried out, there will be a number of actuating bodies lying on the seats in the last valve in the different zones and/or groups of valves. These must normally exit the well again as they could block hydrocarbon flow from the well. It is therefore an advantage that actuating bodies are used which either have a shape or structure that allows them to travel freely back to the surface without coming into conflict with the seats in the valves, or that actuating bodies are used which decompose after a certain time, such that free flow of hydrocarbons can take place from the well.

According to one embodiment, there is also provided a solution to the problem of resetting the valves in the starting position in a safe manner such that they can be used for later subsequent maintenance fracturing jobs. This is done by providing the valve unit with a standardised tool profile to which a suitable tool may be attached. Such attachment can be done in many ways, but a common method will be use of coiled tubing. Then, either all the valves can be opened forcibly by running coiled tubing or they can be closed forcibly. This can, for example, be done by connecting to a profile in the bottom of the counting sleeve and pulling or it up to its end stop where the connection is released. When the counting sleeve has been pulled back to the starting position, it will overcome the friction in the split rings (if these are used). When the counting sleeve has been pulled all the way up/back, it will, e.g., shut off flow out through the openings in the valve unit. In this preferred embodiment, the resetting tool can be run down to the lowermost valve in the well using coiled tubing in order then to be slowly pulled out of the well and at the same time close all the valves in the system and reset them in the starting position in a controlled way as the resetting tool is released when the counting sleeve is drawn back to the starting position.

The opposite function is also conceivable where the position is changed from open to closed by the correct number of actuating bodies counted by the counting sleeve.

According to an embodiment, the invention provides the possibility of reuse of the valves in that they can be remotely opened without using well tools. By virtue of the design of the valve and the counting sleeve, it will be possible to reuse the valve's counting function when resetting the system to the starting position, either with the aid of a well tool as mentioned, or by using a ball that actuates a reset function. Normal time intervals between fracturing jobs are typically 4-5 years, which means that the savings also on reuse are substantial.

Other equally relevant uses may comprise, but are not limited to: actuating well perforating guns, actuating other types of well inflow valves, injection valves for chemicals, gas lift valves and so-called sliding sleeves. It should be understood that valves are only an example of the use of the actuation mechanism/system. To the extent the terms “actuation mechanism/system” and “valve” or “valve unit” are used, sometimes interchangeably, “valve” or “valve unit” should only be regarded as an example of the actuation mechanism/system according to the invention.

To prevent hardening and blocking up during and after use of, e.g., cement, a suitable lubricant/grease comprising sugar or the like can be used. The sugar added to the lubricant will prevent the cement from hardening in the area where the lubricant is located, but will not prevent hardening of the cement/concrete that passes the lubricant.

According to an embodiment, a lower seat that is established can comprise a split ring 60 that is compressed instead of an annular ring seat 4, so as to thus form a split ring seat 70. This may be a part of the counting sleeve or a separate part that is pushed down by the final axial movement of the counting sleeve. The last ball that passes will actuate the split ring seat before it is released from the counting sleeve's last annular ball seat, after which the ball lands on the underlying split ring seat (FIG. 18).

The lowermost seat may alternatively have other designs, for example, dogs, crescents or other suitable geometries.

A gasket (not shown) that secures additional sealing between the ball and the final seat may advantageously be used. It is an alternative that the last seat is held in place until actuation with the aid of, e.g., a shear pin or split ring, such that it does not move into an active position during vibrations, handling, during running in the well or because of previously passed balls.

The valve or pipe section 1 can preferably be produced in any material suitable for installation in a well, and as a non-exhaustive example mention may be made of some types of steel used, such as ASI 4113, 420 mod 13% Cr, super duplex or high-grade steel such as Inconel 718. It is also conceivable that ceramic materials and other composite materials may be used.

The advantage of having such an underlying seat after the valve has been opened, is that a larger contact surface between the ball and the counting sleeve can be obtained than will be provided by the rings of ball seat elements. It is thus possible to obtain greater pressure tolerance and better sealing between the ball and the seat, such that less fluid flows past and down to zones below.

According to an embodiment, there is provided a tubing-mounted downhole actuation system, which is designed to be actuated by means of an axial, displacing movement of a counting sleeve 2, where the counting sleeve 2 is arranged in a pipe section 1 of a well, the pipe section 1 forming a housing for the counting sleeve 2, where the counting sleeve 2 comprises an interior surface and an exterior surface, the interior surface of the counting sleeve forming a part of the wellbore 101, where the counting sleeve's 2 axial, displacing actuating movement is designed to be initiated by an actuating body 3 that passes through the actuation system through the wellbore 101. The counting sleeve 2 comprises a circumferential row of holes 6 in which one or more ball seat elements 5 are arranged, the ball seat elements 5 being capable of taking up at least two positions, one first active, projecting position 80 in which the ball seat elements 5 project into the wellbore 101, and one second passive, retracted position in which the ball seat elements are retracted relative to the wellbore 101, the ball seat elements 5 in their projecting position forming an annular ball seat 4 that is designed to form a seat for the actuating body.

According to another embodiment, the actuating body 3 may comprise a ball.

According to another embodiment, the actuating body may be decomposable.

According to another embodiment, the counting sleeve 2 may be designed to start and carry out its axial movement when the actuating body 3 lands on the annular ball seat whilst the ball seat elements are in their first projecting position 80.

According to another embodiment, the counting sleeve can be designed to end and stop its axial movement when the ball seat elements that form the annular ball seat 4 retract to and take up their second retracted position, after which the ball 3 is released and allowed to move further down in the well 101.

According to another embodiment, the counting sleeve can comprise two or more circumferential rows of holes 6 in which one or more ball seat elements 5 are arranged.

According to another embodiment, the counting sleeve can comprise a final ball seat comprising a split ring 60, this being designed to rest on one or more shoulders 50 and be compressed to an inner diameter that is smaller than the diameter D of a ball.

According to another embodiment, two or more circumferential rows of holes 6, in which one or more ball seat elements are arranged, may form a potential annular ball seat 4.

According to another embodiment, only one row of holes 6 forms one annular ball seat 4 at a time.

According to another embodiment, the actuation system is designed to form a new annular ball seat 4 when the actuating body has axially displaced the counting sleeve a predetermined distance A.

According to another embodiment, the predetermined distance A can correspond to the distance between two radial, circumferential rows of holes in which one or more ball seat elements are arranged.

According to another embodiment, the first active projecting position 80 can be taken up with the aid of a constriction 30 in the pipe section 1 outside the counting sleeve 2, an axial movement of the counting sleeve 2 and the constriction 30 helping to force the ball seat elements 50 into the wellbore and into the first active, projecting position 80, from a second passive, retracted position, in order there to form an annular ball seat 4 when a row of radial, circumferential holes 6 comprising ball seat elements 5 that form an annular ball seat 4 pass the constriction 30.

According to another embodiment, the second passive, retracted position can be taken up when a row of radial, circumferential holes 6 comprising ball seat elements 5 passes the constriction, an axial movement of the counting sleeve helping to release the ball seat elements from a second passive, retracted position into a first active, projecting position 80, in which the ball seat elements project into the wellbore 101, when a row of radial, circumferential holes 6 comprising ball seat elements 5 passes the constriction or cam 30.

According to another embodiment, the counting sleeve can comprise additional circumferentially arranged holes comprising ball seat elements 14, the distance between the additional radial, circumferential holes and an underlying annular ball seat being adapted such that a ball lying on the annular ball seat will press the ball seat elements out of the wellbore and into external grooves 15 provided in the pipe section forming a housing for the counting sleeve.

According to another embodiment, the ball seat elements 14 that are arranged in the additional circumferentially arranged holes and are pressed into the external grooves 15 can prevent rotation of the counting sleeve.

According to another embodiment, the ball seat elements 14 that are arranged in the additional circumferentially arranged holes and are pressed into the external grooves 15 can prevent the axial displacement of the counting sleeve from being limited by adaptation of the length of the grooves, the grooves in the downward, axial direction ending when the underlying annular ball seat 4 has been established, the termination of the grooves 15 forming seats for the ball 14.

According to another embodiment, the ball seat elements 14 can be released into the wellbore and out of the grooves 15 when the ball 3 that forces them into the grooves has been dropped further down in the well.

According to another embodiment, there can, between the counting sleeve and the pipe section therearound and above and below the constriction, be provided space that give sufficient room for ball seat elements 5; 14 when they are to be in the retracted position.

According to another embodiment, the number of rows of radial, circumferential holes comprising ball seat elements 5 that are to form annular ball seats 4, can correspond to the number of balls it is desired should pass before the actuation system is triggered or actuated.

According to another embodiment, between the counting sleeve and the pipe section therearound, there can be provided friction elements 17; 18 that control, brake and/or stop the axial movement of the counting sleeve, the friction elements consisting of at least one of the group comprising: split ring, a rough surface, a coating, ridges, c-clip rings, shear rings, shear pins.

According to another embodiment, at least one internal profile may be provided.

According to another embodiment, at least one internal profile can be adapted for engagement with a tool that is adapted to grip the profile and reset the actuation system in the starting position.

According to another embodiment, at least one internal profile can be adapted for engagement with a tool that is designed to grip the profile and set the actuation system in a desired position.

According to another embodiment, at least one internal profile can be adapted for engagement with a tool that is designed to grip the profile and forcibly actuate the actuation system.

According to another embodiment, the actuation system can help to open a valve that provides communication between the interior and the exterior of the wellbore.

According to another embodiment, the actuation system can help to close a valve that closes off communication between the interior and the exterior of the wellbore.

According to another embodiment, the actuation system can help to initiate a function or operation.

According to another embodiment, the counting sleeve 2 can engage and actuate an underlying seat 70 for the actuating body 3.

According to another embodiment, the underlying seat 70 for the actuating body 3 can comprise a split ring 60.

According to another embodiment, the underlying seat can comprise a gasket against the actuating body 3.

According to embodiments described herein, it is thus provided a downhole actuation system that does not create restrictions or a successive narrowing downward in the well, where the actuation system can be used to actuate different types of functions or operations. Advantageously, the system can be designed to allow a ball of the same size to be used to open and/or close all valves in a desired sequence. According to embodiments described herein, an actuation system that is reliable, comprises few moving parts, is not sensitive to contaminants or impurities in the well fluid is provided. If desirable, the system can be so arranged as to allow repeated usage and/or be reset.

In an embodiment, illustrated in FIGS. 22 and 23, there is provided a downhole actuation system having a counting sleeve 2 arranged in a pipe section. The pipe section 1 forms a housing for the counting sleeve 2, which is designed to be moved axially by means of an actuating body 3 (equivalently as shown in FIGS. 19 and 21) which can be passed through the pipe section 1. The counting sleeve 2 comprises a plurality of radial openings, in this case four openings, in which seat elements in the form of c-rings 42 a-d are arranged. The c-rings 42 a-d have a passive, disengaged position in which they are spaced from the internal through-channel of the sleeve 2, and an active, engaged position where they are engaged by a cam 30 (equivalently as shown in FIGS. 19-21) and pushed partly into the through-channel. A part of the c-rings 42 a-d which extend into the through-channel form an annular seat configured to engage and support the actuating body 3.

In the embodiment shown in FIGS. 22 and 23, four c-rings 42 a-d are used, however the system may be designed with more or fewer c-rings. In this embodiment, four activation bodies 3 (e.g., activation balls) need to be passed through the counting sleeve 2 before fluid ports 40 in the sleeve 2 align with fluid ports 41 in the pipe section 1 so as to provide fluid communication between the inside and the outside of the pipe section 1. 

1. A downhole actuation system, designed to be actuated by an axial movement of a counting sleeve, where the counting sleeve is arranged in a pipe section in a well, the pipe section forming a housing for the counting sleeve, where the axial movement of the counting sleeve is designed to be initiated by an actuating body in the pipe section, wherein the counting sleeve comprises: at least one radial opening in which at least one seat element is arranged, the at least one seat element being capable of taking up a first, active position in which the at least one seat element projects into a longitudinal through-channel of the counting sleeve and a second, passive position in which the at least one seat element is retracted from the through-channel, the at least one seat element in its first position forming an annular seat configured to engage the actuating body.
 2. The actuation system according to claim 1, wherein the at least one seat element is an elongate element arranged along an inner circumference of the counting sleeve.
 3. The actuation system according to claim 2, wherein the at least one seat element is a split ring.
 4. The actuation system according to claim 3, wherein the split ring is a C-ring.
 5. The actuation system according to claim 1, wherein the at least one radial opening comprises a plurality of holes arranged circumferentially around the counting sleeve, wherein each hole has a seat element arranged therein.
 6. The actuation system according to claim 1, wherein the actuating body is a ball.
 7. The actuation system according to claim 1, wherein the actuating body is decomposable.
 8. The actuation system according to claim 1, wherein the counting sleeve is configured to start and carry out its axial movement when the actuating body lands on the annular seat whilst the at least one seat element is in its first position.
 9. The actuation system according to claim 1, wherein the counting sleeve is configured to end and stop its axial movement when the at least one seat element that forms the annular seat retracts to the second position, whereby the actuating body is released and allowed to move further down in the well.
 10. The actuation system according to claim 1, wherein the counting sleeve further comprises two or more longitudinally spaced radial openings, each of which having at least one seat element arranged therein.
 11. The actuation system according to claim 10, wherein the counting sleeve comprises a final seat, the final seat comprising: a split ring, the split ring being configured to rest on one or more shoulders and to be compressed to an inner diameter that is smaller than the diameter of the actuating body.
 12. The actuation system according to claim 10, wherein the actuation system is configured to form a new annular seat when the actuating body has axially displaced the counting sleeve a predetermined distance.
 13. The actuation system according to claim 12, wherein the predetermined distance corresponds to the distance between two rows of holes in which one or more seat elements are arranged.
 14. The actuation system according to claim 1, comprising a cam in the pipe section outside the counting sleeve, the cam configured to engage the at least one seat element and bring the at least one seat element: from the first position to the second position, and/or from the second position to the first position.
 15. The actuation system according to claim 5, wherein the counting sleeve comprises additional circumferentially arranged holes comprising ball seat elements, the distance between the additional circumferentially arranged holes and an underlying annular ball seat being adapted such that a ball lying on the annular ball seat will press the ball seat elements out of the wellbore and into external grooves provided in the pipe section forming a housing for the counting sleeve.
 16. The actuation system according to claim 15, wherein the ball seat elements that are arranged in the additional circumferentially arranged holes and are pressed into the external grooves are configured to prevent rotation of the counting sleeve.
 17. The actuation system according to claim 16, wherein the ball seat elements that are arranged in the additional circumferentially arranged holes and are pressed into the external grooves prevent axial displacement of the counting sleeve over a limited distance by adaptation of the length of the grooves, the grooves in a downward axial direction ending when the underlying annular seat has been established, the termination of the grooves forming seats for the ball seat elements.
 18. The actuation system according to claim 15, wherein the ball seat elements are released into the wellbore and out of the grooves when the actuating body that forces them into the grooves has been dropped further down in the well.
 19. The actuation system according to claim 1, wherein the number of sets of longitudinally spaced radial openings corresponds to the number of actuating bodies which is desired should pass before the actuation system is triggered or actuated.
 20. The actuation system according to claim 1, further comprising friction elements arranged between the counting sleeve and the pipe section, the friction elements configured to control, brake and/or stop the axial movement of the counting sleeve, the friction elements consisting of at least one of: a split ring, a rough surface, a coating, ridges, c-clip rings, shear rings, or shear pins. 